The F-328A is a 5 KW, water-cooled triode with a mu of 16 and a maximum frequency of 3 MHz that was made by Federal Telegraph. The F-328B is the same tube with a two section filament. This example is the early version of the tube with the flying leads and was used by 6AM (W6AM) ca. 1927 and may have been rebuilt by the National Radio Co. (6EX). The tube came with the original home made water jacket with the ends of the petrified hoses attached. The water jacket has a spring loaded contact in the bottom that is internally straped to the side for a plate connection. A soldering lug on one of the nuts on top of the jacket was the connection.
Length = 21.00" Diameter = 3.37"
Max voltage = 8000
Max current = 1 amp
Fil voltage = 21.5
Fil current = 41 amps